#include <iostream>
#include <set>
using namespace std;

int w, h, n;
set<int> wm, hm;

int main()
{
	cin >> w >> h >> n;
	for ( int i = 0; i < n; i++ ) {
		int s, k;
		cin >> s >> k;
		wm.insert(s);
		hm.insert(k);
	}

	cout << ((long long)wm.size() * h + (long long)hm.size() * (w - wm.size()) - n) << endl;

	return 0;
}